1. Field of the Invention
The present invention relates to a two-piece solid golf ball having a cover formed from a polyurethane material; and more particularly to a golf ball which provides a satisfactory feeling on impact and excellent controllability, which exhibits excellent cut resistance (i.e., durability when topped with an iron), scuff resistance, and durability against cracking caused by repeated hitting, and which is suitable for use by advanced golfers on golf practice ranges.
2. Description of the Related Art
Conventionally, in many cases, one-piece balls have been used on golf practice ranges (hereinafter the expression “balls used on golf practice ranges” will be simplified to “practice golf balls”). However, the total distance of one-piece balls is considerably shorter than that of course balls (i.e., balls used on golf courses). Therefore, when golfers practice with one-piece balls, they cannot acquire an accurate distance sensation that they would acquire in actual games in which course balls are used. One-piece balls are produced from a rubber material cross-linked with zinc methacrylate in order to impart high durability to the balls. However, since the one-piece balls produced from the rubber material exhibit low restitution, their total distance is short.
Conventionally, some two-piece balls have also been used as practice golf balls. However, such practice two-piece golf balls do not meet demands from advanced golfers and professional golfers in terms of controllability (spin performance), although the golf balls exhibit excellent flight performance and provide good feeling on impact. Meanwhile, since the practice two-piece golf balls exhibit poor scuff resistance, the frequency of exchange of the balls is increased. Therefore, from the viewpoint of costs, the practice two-piece golf balls do not meet demands from golf practice range owners.
In order to solve such problems, Japanese Patent Application Laid-Open (kokai) No. 9-215778 discloses a two-piece solid golf ball having a cover formed from a polyurethane material. However, in this golf ball, the thickness of the cover is not appropriate, the restitution of the core is insufficient, and the scuff resistance of the resin used for forming the cover is unsatisfactory. Therefore, the golf ball is not satisfactory as a practice golf ball for advanced golfers.
Meanwhile, Japanese Patent Application Laid-Open (kokai) No. 5-123422 or 6-154357 discloses a two-piece solid golf ball having a thick cover. However, in this golf ball, since the cover is formed from an ionomer resin, the cover is hard, and the scuff resistance of the cover is poor. Therefore, the golf ball does not satisfy advanced golfers in terms of controllability, and does not exhibit sufficient durability required for practice balls.
In order to solve problems involved in the aforementioned conventional golf balls, the present invention provides a golf ball which exhibits controllability (spin performance) comparable to that of a spin-type course ball—although the flight performance is inferior to that of a course ball—which exhibits excellent durability as compared with a course ball, and which is suitable for use by advanced golfers on golf practice ranges.